306 THE OUTGO OF ENERGY 



Connect the electrometer with the secondary 

 coil of the inductorium, and bring the vibrating 

 meniscus into the field. 



Bring the stroboscopic paper next the acid 

 reservoir of the electrometer at such a height 

 that the edge of the meniscus shall be seen 

 through the gray blur. The meniscus will no 

 longer appear blurred, but will be as sharp as 

 if the mercury were stationary. This appearance 

 is produced only when the stroboscopic paper 

 and the object seen by its aid have the same 

 periodicity of vibration. If the periodicity of 

 the vibrations is unequal, interference results, 

 and from this interference the rate of vibration 

 of the observed body can be calculated. For 

 example, if the observed body shows three vibra- 

 tions per second, when observed through the 

 stroboscope, its rate is three more per second 

 than that of the stroboscope. 



In the present instance, the meniscus remains 

 apparently at rest. The number of action cur- 

 rents is therefore identical with the number of 

 stimuli. 



2. RTieoscopic Muscle Tetanus. The same 

 method may be applied to the analysis of the 

 rheoscopic tetanus in the rheoscopic muscle. 



Place two nerve-muscle preparations in the 

 moist chamber. Place the tendon of muscle B 



